Method of manufacturing a composite article having a high clarity icon and the product produced by the method

ABSTRACT

A method of manufacturing an injection molded object having an outer shell with a front face and a light transmitting assembly molded into the outer shell which assembly is visible from the front face. The method includes the following steps. Supporting a light transmitting assembly on a mold projecting tool which is closable with a mold cavity tool having an interior wall which defines the front wall of the outer shell. Forming narrow passages through the light transmitting assembly to connect its front and rear faces. Closing the mold to position the front face of the light transmitting assembly adjacent the interior wall of the mold cavity tool while leaving a narrow peripheral recess therearound in communication with the narrow passages. Injecting a molten plastic into the closed mold to form the outer shell of the object while also flowing the molten plastic through the narrow passages in the light transmitting assembly and the narrow peripheral recess between the front face of the light transmitting assembly and the interior wall of the mold projecting tool. Separating the injected plastic filling the narrow passages of the light transmitting assembly from the injected plastic filling the narrow recess upon separation of the mold projecting tool and the mold cavity tool.

This application is a continuation-in-part of my application Serial No.08/583,522, filed Jan. 5, 1996 titled Method of Manufacturing acomposite article having a high clarity icon and the article produced bythe method, now U.S. Pat. No. 5,641,556.

BACKGROUND AND SUMMARY OF THE INVENTION

This invention is directed to an improvement in the method ofmanufacturing a composite article having a high clarity icon and animproved article produced by the method. My prior method and article aredisclosed in my co-pending patent application Serial No. 08/583,522,filed Jan. 5, 1996, and assigned to the same assignee as thisapplication, which patent application is incorporated herein byreference. One aspect of my previous method involved the injectionmolding of an opaque plastic from the rear surface of a compositearticle through passages formed in a light transmitting anvil and a coreto assist in forming a thin front layer of opaque plastic around thefront of the icon without forming what are called "weld lines" which mayoccur when a molten plastic is flowed in a thin layer over a relativelywide area. When more complex icons are created, especially icons formedof a string of letters creating a word, the icon so formed is morelikely to be elongated in one direction thus requiring passages in theanvil to be spaced along the elongated dimension of the compositearticle. To properly supply a molten plastic to these passages, a spruerunner is provided across the base of the light transmitting anvil. Inthe completed composite article, such a runner would obstruct thepassage of light through the light transmitting anvil and core.

Therefore, an object of this invention is a method of manufacturing acomposite article having an icon in its front face which method permitsthe formation of a thin layer of plastic over the front face of thecomposite article, which article is elongated in at least one dimension,by flowing the molten plastic through passages formed in a lighttransmitting anvil and core without diminishing the light transmittingqualities of the icon formed in the front face of the article.

Another object of this invention is a method of removing the moltenopaque plastic deposited in the passages of a light transmitting anvilin a composite article without disturbing the thin layer of plasticdeposited over the front face of the composite article surrounding anicon.

A further object of this invention is a method of removing the moltenopaque plastic deposited in the passages of the light transmitting anviland contained in a sprue runner which is attached to the depositedplastic and ejecting the plastic during the molding process.

Yet another object of this invention is a composite plastic objecthaving an elongated icon on the front face of the object which icon issurrounded by a thin opaque layer of plastic which is free of "weldlines".

Still another object of this invention is a composite plastic objecthaving a backlighted elongated icon which is interlocked with its outershell without significant loss of its light transmitting ability.

Other objects may be found in the following specification, claims anddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is illustrated more or less diagrammatically in thefollowing drawings wherein:

FIG. 1 is a top plan view of a plastic article such as a button made inaccordance with the teachings of this invention with some hidden partsshown in dashed lines;

FIG. 2 is a side elevational view of the button of FIG. 1 with somehidden parts shown in dashed lines;

FIG. 3 is a cross sectional, somewhat schematic representation of a moldtool for molding the article of FIGS. 1 and 2, shown in an open positionwith a core and anvil carried by the tool;

FIG. 4 shows the mold tool of FIG. 3 in its closed position with theplastic forming the outer shell of the composite article injected intothe mold;

FIG. 5 is a partial view of the molding tool of FIG. 4 with the finishedcomposite article retracted from the mold;

FIG. 6 is a cross sectional view of the finished molded compositearticle;

FIG. 7 is a partial cross sectional view showing the removal of thesprue runner from the finished composite article; and

FIG. 8 is a partial cross sectional view showing a step in the removalof the sprue runner from one of the molding tools.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1, 2 and 6 of the drawings show the invention embodied in a button11 which, by way of example and not by way of limitation, may be of thetype which is installed on the dashboard of a motor vehicle. Theinvention can also be applied to a variety of composite injection moldedplastic articles, especially those in which light is to be transmittedthrough icons of otherwise opaque structures. The button 11 of thisinvention includes an opaque shell 13 which is somewhat elliptical intransverse cross section. The shell includes a front wall 15 of somewhatelliptical shape and a rearwardly opening cavity 17 terminating in anannular peripheral base 19. An outer, half high skirt 21 is upstandingon the annular base 19 to partially surround the opaque shell 13. Ribs23 are molded integrally between the shell 13 and the outer skirt 21.Mounting pins 25 extend downwardly as viewed in the drawings from theannular base 19 as does an actuation plate 27 for an electric switch(not shown). The mounting pins may be fitted into spring loaded socketsto mount the button 11.

Formed on the front wall 15 of the button 11 is an icon 31 forming theword "MIRROR". This icon must be visible to the user both in naturallight such as in the daytime and under darkened conditions and,therefore, is backlighted. The term "icon", as used in the specificationand claims, encompasses not only words, such as the word "MIRROR" shownin FIG. 1 of the drawings, but also includes graphic configurations,numerals, indicator lines, trademarks, logos, symbols and any other typeof a representation which conveys information to or can be recognized bya user.

The button 11 and its icon 31 are built around a core 33 which has afront face 35 formed on a front wall 37, a rear face 39, depending sidewalls 41 and depending end walls (not shown). This core includes asportions of its front wall 37, imperforate portions 45 and perforateportions 47 which together create the design of the stencil 49 whichdefines the icon 31. In this embodiment of the invention, theimperforate portions 45 create the letters of the word "MIRROR" but someof what would normally be perforate portions between the letters arecovered by a thin, translucent, plastic membrane for reinforcingpurposes, which membrane is not shown in the drawings for clarity ofillustration. To maintain the clarity of the word "MIRROR", the onlyperforate portions 47 provided in core 33 are located so that theyextend through the openings in the "O" and in the "R"s of the word"MIRROR".

The core 33 in this embodiment is formed of a white plastic such as anacetal with some of its imperforate portions 45 having fine definitionsand thicknesses of only slightly more than ten-one thousandths of aninch. A plastic core molded to such fine definitions and minimumdimensions has been obtained by using electroerosive metal cuttingtechniques to form the molds and tooling used to create parts such asthe core 33, especially the imperforate portions 45 and perforateportions 47 of the stencil 49. The use of electroerosive metal cuttingtechniques increases the definition of the portions forming the stencilby eliminating the concave and convex fillets in molds and tools formedby conventional cutting equipment.

To provide additional support for the stencil 49 during subsequentmolding operations, an anvil 61 is provided. The anvil 61 of thisembodiment of the invention is formed of a light transmittingpolycarbonate to enable the anvil to also function as a light pipe tobacklight the icon 31. The anvil 61 is formed with a downwardlyextending (as viewed in the drawings) rib 63 extending along one endthereof, a front face 65 and a rear face 67. Supporting surfaces 69 areformed on the upper ends of projections 71 extending from the front face65. Although not shown in the drawings for clarity of illustration,longitudinally extending ribs are provided between the projections 71and these longitudinally extending ribs terminate slightly below thesupporting surfaces 69 of the projections 71. End shoulders 75 areintegrally formed on the anvil. Tapered passages 77 are formed throughthe anvil 61 and are aligned with passages 79 extending through theprojections 71. The passages 79 are wider than the tapered passages 77thus forming shoulders 81 at the boundaries between the passages 77 andthe passages 79.

FIGS. 3, 4, 5, 7 and 8 of the drawings show, in a schematic manner forclarity of illustration and explanation, a mold tooling 91 havingcomplementary cavity and projection tools. The mold tooling 91 includesa first mold cavity 93 having an interior wall 95 which defines theopaque shell 13 of the button 11. For clarity of illustration andexplanation, some of the elements of the mold tooling forming thevarious details of the button 11 have been omitted from the drawings.Also formed on the interior wall 95 of the mold cavity 93 and projectinginwardly thereof is an icon shielding tool 97. The icon shielding toolhas facing surfaces which are the same shape, but slightly smaller, thanthe imperforate portions 45 of the stencil 49 which defines the icon 31.This smaller "footprint" of the icon shielding tool provides a recess 99in the mold cavity 93, most clearly shown in FIGS. 3, 4, 5 and 6 of thedrawings, around the peripheries of the imperforate portions 45 of thestencil. The icon shielding tool 97 prevents the later injected opaqueplastic from flowing over and filling in the imperforate portions 45 ofthe stencil while allowing the opaque plastic to fill the recess 99 andthus form narrow borders 100 around the letters forming the icon. Thenarrow borders 100 surround the letters of the icon 31 to tightlyencapsulate the stencil 49 while still sharply delineating the icon 31.A gate 101 is formed in the interior wall 95 of the mold cavity 93 andleads to a sprue passage 103 in the mold cavity tool.

A mold projection tool 115 is formed with a well 117 defined by a bottomwall 119, end walls 121 and 123 and side walls, one of which, side wall125, is shown in the drawings, to receive and support the anvil 61 withthe end shoulders 75 of the anvil resting on and being supported by theend walls 121 and 123 of the mold projection tool. The rib 63 of theanvil engages the bottom wall 119 of the well and obstructs the end wall121 thereof. A passage 127 extends through the end wall 123 to allow theflow of molten plastic against the rear face 67 and rib 63 of the anvil61 to form a chamber 129 which defines a sprue runner 131. The passage127 is formed with a sloped upper wall 133 which forms a complementarysloped wall 134 on the sprue runner for assisting in removing the spruerunner 131 in a manner to be hereinafter described.

In manufacturing the button 11 of this invention, the core 33 ispositioned on the anvil 61 and both are mounted on the mold projectiontool 115 as shown in FIG. 3 of the drawings. Then the mold is closed andthe molten plastic is injected into the mold cavity 93 through a sprue141, sprue passage 103 and gate 101. The molten opaque plastic thenflows around the mold projection tool 115 and against the interior wall95 of the mold tool to form the front wall 15 and the remainder of theshell 13 of the button 11. It also flows into the recess 99 between thecore 33 and the interior wall 95 of the mold cavity 93. Molten plasticalso flows through the passage 127 in the end wall 123 of the moldprojection tool to fill the chamber 129 formed between the moldprojection tool 115, the rear face 67 and the downwardly extending rib63 of the anvil 61. The molten plastic then flows through the taperedpassages 77 formed in the anvil 61 and into the passages 79 formed inthe projections 71 of the anvil 61 to fill the spaces between theprojections and the stencil 49.

Upon retraction of the mold projection tool 115 from the mold cavity 93as shown in FIG. 5 of the drawings, the sprue nozzle 103 is separatedfrom the shell 13 at the gate 101 of the mold cavity. As the moldprojection tool continues to retract, knockout pins (not shown) arrestmovement of the button 11, allowing the mold projection tool to separatefrom the newly formed button taking the sprue runner 131 and theprotuberances 143 of plastic that formerly filled the tapered passages77 of the anvil 61 away with the runner as shown in FIG. 7 of thedrawings. The protuberances 143 separate from the molten plasticoriginally injected into the tapered passages 77 and passages 79 at theshoulders 81 between these passages. Thus, the plastic 145 is retainedin the passages 79 formed in the projections 71 of the anvil 61.Continued retracting movement of the mold tool 115 brings ejector pins(not shown) in contact with the sprue runner 131 and attachedprotuberances 143 to move the sprue runner laterally, as shown in FIG. 8of the drawings, into the void space formerly occupied by the downwardlyextending rib 63 of the anvil 61. This movement to the left as viewed inFIGS. 7 and 8 of the drawings moves the sloped end wall 134 of the spruerunner out of the passage 127 in the mold projection tool to allow thesprue runner to be ejected.

As can be seen in FIG. 6 of the drawings, the button 11 in its finishedform has an anvil 61 with sprue runners and protuberances 143 ofinjected plastic removed to provided maximum light passage through theanvil and its projections to the imperforate portions 45 of the corewhich provide the image of the icon 31 when viewed from the front faceof the button 11. The injection molded plastic 145 remaining in thepassages 79 formed in the projections additionally interlocks the anvilwith the core and with the opaque shell 13 of the button as do theshoulders 81 of the anvil.

I claim:
 1. A method of manufacturing an injection molded object havingan opaque outer shell with a front face and a light transmittingassembly molded into said opaque outer shell and at least partiallyvisible from said front face, said method including the stepsof:supporting a light transmitting assembly having front and rear faceson a mold tool which is positioned to be closable with a complementarymold tool upon movement of said mold tools towards each other, saidcomplementary mold tool having an interior wall which defines said frontface of said opaque outer shell, forming passages through said lighttransmitting assembly to extend between said front and rear facesthereof, bringing said mold tools together to close said mold and toposition said front face of said light transmitting assembly adjacentsaid interior wall of said complementary mold tool, injecting a moltenplastic into said closed mold to form said opaque outer shell of saidobject while also flowing said molten plastic through said passages insaid light transmitting assembly to form a layer of opaque plastic onsaid front face of said light transmitting assembly around saidpassages, and separating at least a portion of said injected opaqueplastic filling said passages of said light transmitting assembly uponseparation of said mold tools to reduce the amount of opaque plasticavailable to obstruct the passage of light through said lighttransmitting assembly.
 2. The method of claim 1 including the step offorming an icon on said front face of said light transmitting assemblyand the step of forming a recess around the periphery of said icon whensaid mold tools are brought together to close said mold.
 3. The methodof claim 1 including the step of ejecting said portion of said separatedinjected plastic filling said narrow passages from said mold tool uponseparation of said mold tools.
 4. The method of claim 1 in which saidlight transmitting assembly includes a core having said front face andan anvil having said rear face with an icon formed on said front face.5. A method of manufacturing a composite object having an opaque outershell with a front face and an interior light transmitting elementhaving a front face and a rear face which light transmitting element isat least partially visible from said front face of the outer shell,including the steps of:forming passages through said light transmittingassembly to provide communication between its front and rear faces,injection molding an opaque plastic around said light transmittingassembly to form said outer shell while also flowing said opaque plasticthrough said passages to fill said passages and to flow opaque plasticover portions of said front face of said light transmitting assemblywhile also forming a sprue runner across said rear face of said lighttransmitting assembly to supply molten plastic to said passages,separating said sprue runner and at least a portion of said opaqueplastic filling said passages from said opaque plastic flowed overportions of said front face of said light transmitting assembly, andejecting said separated sprue runner and said separated portion of saidopaque plastic filling said passages from said outer shell to reduce theobstruction to the passage of light through said light transmittingassembly.
 6. A method of manufacturing a composite article including thesteps of:forming a core having a front face and a rear face with aportion of said front face defining an icon, forming an anvil having asupporting surface in the shape of said portion of said core formingsaid icon and dimensioned to seat on said rear face of said core insupporting engagement with said portion of said core defining said icon,and forming a front face of said composite article by injection moldinga plastic layer over said front face of said core except for at least asubstantial area of said portion of said front face defining said icon.7. The method of claim 6 in said step of forming a front face of saidcomposite article includes the step of seating a tool against said frontface of said core to obturate said portion of front face of said coredefining said icon except for a narrow border therearound.
 8. The methodof claim 2 including the step of connecting said passages and saidrecess around the periphery of said icon when bringing said mold toolstogether to close said mold.
 9. The method of claim 5 in which said stepof forming a sprue runner across said rear face of said lighttransmitting assembly includes the step of forming a sloped wall on saidsprue runner which is engageable by a mold tool to assist in ejectingsaid separated sprue runner and said portion of said plastic fillingsaid passages from said outer shell.